Eye treatment system with fluidics pump interface

ABSTRACT

An eye treatment system for performing an ocular surgical procedure contains an eye treatment probe or handpiece, a treatment console, an eye treatment cassette, and a pump formed by the engagement of the treatment cassette with the treatment console. The handpiece is configured to provide at least irrigation fluid to, and aspiration of fluid from, a subject eye. The treatment console comprises a controller configured to control the eye treatment probe. The eye treatment cassette engages the treatment console to couple the eye treatment probe with the treatment console. The pump comprises a pump head having a plurality of projections disposed to rotate about an axis, a ramp disposed near the rotating projections, and a resilient channel configured to transfer fluid when engaged by the ramp and the plurality of projections. The ramp is configured to reduce pressure fluctuations with the eye during a surgical procedure and comprises and entrance portion, a central portion, and an exit portion. The entrance portion has an arcuate extent over which the projections close the channel as the head rotates. The central portion has an arcuate extent over which the channel is sealed by the projections as the head rotates. The exit portion has an arcuate extent over which the projections open the channel as the head rotates. The ramp is configured such that the arcuate extent of the entrance portion is unequal to the arcuate extent of the exit portion.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to an eye treatment system, and morespecifically to an eye treatment system with an advanced fluidics pumpinterface.

2. Description of the Related Art

Volumetric pumps such as peristaltic pumps are used to remove fluid andother material from a surgical site. For example, in ophthalmic surgicalsystems, volumetric pumps may be used to precisely regulate the flow offluid from the eye during a cataract, vitrectomy, or other surgicalprocedure. Because of the sterile environment necessitated by theseprocedures, portions of the pump and other components of the fluidicsystem, such as valves and sensors, may be configured within adisposable and/or separable fluidics cassette that is replaced orseparately sterilized after a surgery.

In the case of a peristaltic pump, several fingers or rollers arecircularly disposed within a pump head that rotates such that thefingers successively engage a tubing portion through which a fluid ispumped. As the fingers engage the tubing portion, fluid within a volumeof the tubing is entrapped between successive pairs of rollers and sotransferred from an inlet of the pump to an outlet.

One problem encountered with peristaltic and other volumetric pumps isthat as each finger of the pump initially engages the tubing portion,compression of the tubing portion produces a localized pressurevariation that is subsequently transmitted upstream to a surgicalhandpiece and into the eye as a pressure wave. If the pressurefluctuation is too large or sudden, damage to the eye may result.

Various approaches to dealing with unwanted pressure fluctuationsproduced by peristaltic and other types of volumetric pumps have beenproposed, including those disclosed in U.S. Pat. Nos. 5,230,614 and6,962,488, which are herein incorporated by reference. While thesesolutions may work in some surgical systems, other systems place moredemanding challenges to the mitigation of pressure fluctuation. Suchdemands include tight cassette packaging constraints, the use ofmultiple pumps in a single cassette, or orientation of the pump withinthe cassette.

Because of the increasing demands produced by advances surgical andother fluidics systems, there is a need for more advanced solutions inmitigating the occurrence of pressure fluctuations produced byvolumetric pumps.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention may be better understood from thefollowing detailed description when read in conjunction with theaccompanying drawings. Such embodiments, which are for illustrativepurposes only, depict the novel and non-obvious aspects of theinvention. The drawings include the following listed figures:

FIG. 1 is system diagram of a surgical system for use on the eye of asubject according to embodiments of the invention.

FIG. 2 is a block diagram of portions of a surgical system according toembodiments of the invention including two volumetric pumps and a vacuumsystem.

FIG. 3 is a block diagram of portions of a surgical system according toembodiments of the invention including one volumetric pump and a vacuumsystem.

FIG. 4 is a perspective view of the surgical system illustrated in FIG.2 showing a fluidics cassette separated from a surgical console.

FIG. 5 is a front view of the surgical console shown in FIG. 4.

FIG. 6 is a perspective view of the surgical system illustrated in FIG.4 showing the cassette coupled to the surgical console.

FIG. 7 is an exploded view of the cassette shown in FIG. 4.

FIG. 8 is portion of a resilient channel shown in FIG. 7 in astraightened form.

FIG. 9 is a top view of a portion of the surgical system shown in FIG.4.

FIG. 10 is a top view of a portion of the surgical system shown in FIG.4 illustrating the cassette coupled to the surgical console.

FIG. 11 is a front perspective view of the cassette shown in FIG. 4.

FIG. 12 is a rear perspective view of the cassette shown in FIG. 4.

FIG. 13 is a top view of the cassette shown in FIG. 4 illustratingvarious feature of a ramp according to embodiments of the presentinvention that is configured to reduce pressure fluctuations at an inputinto a volumetric pump.

FIG. 14 is a block diagram of a method according to an embodiment of thepresent invention.

FIGS. 15A-15C are diagrams illustrating a method of operation of a pumpaccording to embodiments of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

The present invention is generally directed to systems utilizingvolumetric pumps configured to reduce or eliminate pressure fluctuationsat the pump entrance. Embodiments of the present invention may findparticular use in eye treatment systems where pressure fluctuations atthe pump entrance can be propagated upstream to eye, potentiallyresulting in unwanted damages. Without wishing to limit the scopethereof, embodiments of the present invention will be discussed withregard to a system for treating an eye of a patient. It will beappreciated that embodiments of the invention may also be applied toother systems, including other surgical system for use in performingprocedures on other parts of the body of a subject.

Referring to FIG. 1, a surgical system 20 generally comprises an eyetreatment probe or handpiece 22 that is coupled to a console 24 by acassette 26 configured to supply irrigation and aspiration functions tothe handpiece 22. Handpiece 22 generally includes a handle or grippingportion for manually manipulating and supporting an insertable probetip. The probe tip includes a distal end that is insertable into an eyeE of a patient P, with one or more lumens in the probe tip allowingirrigation fluid to flow into the eye E. Aspiration fluid may also bewithdrawn through a lumen of the probe tip, with the console 24 and/orthe cassette 26 generally including a vacuum aspiration source, apositive displacement or volumetric aspiration pump, or both. Flexibleconduits 28 of the cassette 26 help avoid direct contact betweenirrigation and aspiration fluids flowing to or from the eye and thecomponents of console 24.

When the distal end of the probe tip of handpiece 22 is inserted intothe eye E, an electrical conductor and/or pneumatic line (not shown) mayalso be provided between the console 24 and the handpiece 22. Forexample, to enable phacoemulsification of the natural lens in the eye E,an electrical line may be included to provide power from the console 24to drive a piezoelectric device located in the handpiece 22. Thispiezoelectric device helps to fragment the tissue of the lens, which canthen be drawn into a port of the tip by aspiration flow. In otherembodiments, the handpiece 22 is configured to remove vitreous materialin the posterior chamber of the eye E, for example, by including anelectrically or pneumatically driven cutter blade. In any case, acontroller 30 in the console 24 is generally included to control thevolume of material removed by the aspiration flow, regulate irrigationflow through handpiece 22 (or a separate probe structure), manageelectrical and/or pneumatic drivers connected to the handpiece 22,and/or receive one or more input signals from sensors for monitoring thestate of the system 20 during a surgical procedure.

The controller 30 may include an embedded micro-controller and/or manyof the components typically found a personal computer, such as amicro-processor, data bus, memory chips, input devices, and/or outputdrivers. The controller 30 may also include a user interface 31 and/or afoot pedal input device (not shown), and the like. Controller 30 maygenerally include hardware, firmware, and/or software capabilities, withthe software and/or firmware typically comprising machine readable codeor programming instructions for implementing one, some, or all of themethods described herein. The code may be embodied by a tangible mediasuch as a memory, a magnetic recording media, an optical recordingmedia, or the like. Controller 30 may have (or be coupled to) arecording media reader, or the code may be transmitted to controller 30by a network connection such as an internet, an intranet, an Ethernet™,a wireless network, or the like. Along with programming code, controller30 may include stored data or correlations for implementing the methodsdescribed herein, and may generate and/or store data that recordsparameters corresponding to the treatment of one or more patients. Manycomponents of console 24 may be found in or modified from knowncommercial phacoemulsification systems from Advanced Medical Optics Inc.of Santa Ana, Calif.; Alcon Manufacturing, Ltd. of Fort Worth, Tex.;Bausch and Lomb of Rochester, N.Y.; and other suppliers.

FIG. 2 is a schematic representation of a cassette 26 a according to anembodiment of the invention that is disposed within a cassette frame,housing, or body 32 and having elements that interface with the console24, for example, to couple the console 24 to the handpiece 22. Anirrigation bottle, container, or source 34 may be used to provideirrigation fluid pressure, for example, by relying at least in part on agravity pressure head that varies with a height of the irrigation source34 or the like. An irrigation on/off pinch valve 36 may include a shortsegment of a resilient flexible conduit 36 a within the cassette 26 a,which can be engaged and actuated by an actuator of the console 24. Asurface of the cassette body 32 may be disposed opposite the actuator tofacilitate closure of the conduit segment. Alternative irrigation flowsystems might include pumps, alternative fluid pressurization drivesystems, fluid pressure or flow modulating valves, and/or the like.Regardless, the irrigation network generally defines an irrigation fluidconduit path or line 37 between irrigation source 34 and an irrigationport on the insertable probe tip of handpiece 22. In some embodiments,irrigation fluid from the irrigation source 34 is additionally oralternatively provided to a separate handpiece (not shown) that isdifferent from the handpiece 22.

Aspiration of fluid and other matter from the eye E through anaspiration line 38 may be provided, in conjunction with the cassette 26a, by either a volumetric or peristaltic pump 40 and/or a holding tank44 to which a vacuum is applied via a vacuum source 48. Alternatively,the vacuum source 48 may be directly coupled to the aspiration line 38.In any case, the vacuum source 48 may comprise a Venturi pump and/or arotary vane pump; however, other types of pumps or other vacuum sources(e.g., a vacuum line) may be used in order to produce a desired vacuumlevel in the holding tank 44. In some embodiments, other types of pumpsmay be used to provide aspiration capabilities to the handpiece 22, forexample, a hybrid pump, such as the Concentrix pump by Bausch & Lomb,may be provided that may incorporate capabilities of both a vacuum pumpand a flow pump.

In the illustrated embodiment, the peristaltic pump 40 is formed byengagement of the cassette 26 a with a pump head 50, which may be partof the console 24. The pump head 50 includes one or more rotatingprojections, fingers, or rollers 52 disposed about an axis and near aramp 54 that may be molded or attached to the cassette body 32. The pumphead 50 may be formed within or attached to the cassette body 32. Fluidtransfer by the peristaltic pump 40 is produced as a resilient channel56, in fluid communication with the aspiration line 38, is engaged by orsqueezed between the ramp 54 and one or more of the projections 52. Theresilient channel 56 may be a portion of a tube made of a polymer orother suitable material. Alternatively, the resilient channel 56 may bepart of a molded channel and/or a gland that is squeezed or compressedduring operation of the peristaltic pump 40. As described in greaterdetail below, the ramp 54 may be configured according to embodiments ofthe invention to reduce pressure variations within the aspiration line38 that can be produced when the resilient channel 56 is initiallyengaged by the protrusions 52. Fluid aspirated through the handpiece 22may be deposited in the holding tank 44, regardless of whether theperistaltic pump 40 or the vacuum source 48 is used. A second volumetricor peristaltic pump 60 may be configured as a drain pump thatintermittently transfers fluid from the holding tank 44 to a waste bag62.

During operation, a selector valve 64 may be used to select the sourceof aspiration for the handpiece 22. When the valve 64 is closed, theperistaltic pump 40 may be used for producing aspiration flow from thehandpiece 22, generally independent of the pressure in the holding tank44. Alternatively, the vacuum source 48 may be used in conjunction withthe holding tank 44 to produce aspiration flow by opening the valve 64and halting rotation of the peristaltic pump 40. When peristaltic pump40 is not being operated, at least one of the protrusions 52 pinches offthe arcuate resilient channel 56, thus preventing aspiration flowtherethrough. Material is instead drawn into an aspiration port ofhandpiece 12 via the vacuum source 48 through the open valve 64. In thisoperational mode, the aspiration port draws fluid therein based on thepressure differential between holding tank 44 and the chamber of the eyeE in which the fluid port is disposed. A pressure sensing device orvacuum sensor 66 may be used to determine or estimate an aspirationpressure, flow rate, line deformation, or the like, and to adjustoperation of the peristaltic pump 40 and/or the vacuum source 48 so asto maintain a predetermined flow rate or pressure level at the vacuumsensor 66 or elsewhere within the system. In some embodiments, thevacuum sensor 66 is coupled to the console 24 to provide a pressuresensing mechanism providing an output that is used by the controller 30to control one or more aspects of the system 20.

Referring to FIG. 3, in some embodiments, a cassette 26 b comprises onlythe single peristaltic pump 40, which is available for providingaspiration through the handpiece 22. In the illustrated embodiments ofFIGS. 2 and 3, the cassettes 26 a and 26 b may use a common cassettebody 32 and various other components used in both configurations (e.g.,the vacuum sensor 66). When the cassette 26 b is in this configuration,the valve 64 may be used provide venting or reflux to the handpiece 22.When the valve 64 is open, an equalization pressure is provided betweenthe irrigation and aspiration lines 37, 38, for example during anocclusion of the aspiration tip of the handpiece 22.

FIGS. 4-6 illustrate perspective and front views of a portion of thesystem 20 that is schematically illustrated in FIG. 2, illustratingvarious elements of the console 22 and the cassette 26 a (oralternatively cassette 26 b). For clarity, the handpiece 22 and theirrigation source 34 are not illustrated in the FIGS. 4-6. Referring toFIG. 4, the cassette 26 is shown separated from the console 24, while inFIG. 6 the cassette 26 is shown engaged with the console 24 so as tocouple a handpiece or eye treatment probe with the console 24. FIGS.4-6, illustrate various components of the console 24 and the cassette 26b, including the pump head 50 with the plurality of projections 52thereof.

With particular reference to FIG. 5, the projections 52 may be attachedat one of their ends to a drive plate 50 a and configured to rotateabout an axis A1. The projections may also be commonly joined at theiropposite ends to an attachment plate 50 b, for example, to increaserigidity. The console 24 may also include a second pump head 70 that canbe used in the drain peristaltic pump 60. The second pump head 70comprises projections, fingers, or rollers 72 that are configured torotate about an axis A2. In the illustrated embodiment, the axes A1 andA2 are collinear; however, other relationships between the axes A1 andA2 are possible (e.g., the axes may be parallel to one another,orthogonal to one another, or coplanar).

FIG. 7 is an exploded view of the cassette 26 a. Various components andfluid lines disposed within the cassette body 32 are clearly visible. Inparticular, the resilient channel 56 is seen in an uncompressed stateand arcuately shaped to generally fit along the ramp 54 that is formedin the cassette frame 32. The fluid lines in the illustrated embodimentare in the form of flexible tubing; however, all or portions of thefluid lines of the cassette 26 a (or 26 b) may be replaced other typesof channeling. For example, all or portions of the fluidic lines of thecassette 26 a (or 26 b) may be at least partially replaced by channelsappropriately formed in a cassette frame. In some embodiments, thechannels may be formed by the combination of the cassette frame 32 and aresilient cover, for example, as disclosed in U.S. Pat. No. 6,962,488.

In certain embodiments, the cassette 26 a (or 26 b) comprises first andsecond collars 73 a, 73 b that are disposed along the resilient channel56. Referring to FIG. 8, which shows a portion of the resilient channel56 in a straighten form prior to being configured for mounting in thecassette 26 a (or 26 b), the collars 73 a, 73 b are molded or otherwiseattached to the resilient channel 56 so as to prevent slippagetherebetween. The collars 73 a, 73 b may be separated by a predetermineddistance L that is selected to provide efficient pump performance whenthe resilient channel 56 is mounted to the cassette, for example, byinsertion into receivers 74 a, 74 b, respectively. In the illustratedembodiment, the receivers 74 a, 74 b are located on bosses between whichthe ramp 54 is disposed. In order to help prevent twisting of theresilient channel 56, the collars 73 a, 73 b may be keyed to provide apreferred orientation of the collars within the receivers 74 a, 74 b.The keyed collars 73 a, 73 b may be configured so that they can bemounted only in one orientation within the receivers 74 a, 74 b or maysimply be shaped so that the correct orientation is evident upon visualinspection.

FIGS. 9 and 10 show cutaway top views of the console 24 and the cassette26 particularly illustrating the relationship between the projections 52of the head 50 and the ramp 54 formed in the cassette frame 32. Forclarity, the resilient channel 56 is not shown in FIG. 9. In FIG. 10 theresilient channel 56 is shown compressed between the ramp 54 and two ofthe projections 52 of the pump head 50. The ramp 54 is configured to atleast partially enclose at least some of the projections 52 when thecassette 26 is engaged with the console 24. As seen in FIG. 10, theaspiration pump 40 is formed by the engagement of the cassette 26 withthe console 24. As the projections 52 rotate about the axis A1, fluidand other material is entrapped within a volume 76 of the resilientchannel 56 and transferred from an inlet portion of the peristaltic pump40 to an exit portion thereof. Since the resilient channel 56 is fluidlyconnected to the aspiration line 38, the material is transferred fromthe eye E and through the peristaltic pump 40 as the resilient channel56 is repeatedly engaged by or squeezed between the ramp 54 and theplurality of projections 52. As discussed in greater detail below, theprofile of the ramp 54 may be configured mitigate or substantiallyeliminate large and/or rapid variations in the pressure of theaspiration line 38 as each of the projections 52 initially engages andsubsequently squeezes the resilient channel 56.

FIGS. 11 and 12 illustrate the cassette 26 with associated components ofthe system 20, including but not limited to, irrigation inlet and outletlines 37 a, 37 b, aspiration line 38, waste bag 62, holding tank 44, andvacuum sensor 66. In other embodiments, the same cassette body 32 may beconfigured for use with only the aspiration peristaltic pump 40, asdiscussed in relation to the system schematically illustrated in FIG. 3.The irrigation and aspiration lines 37 b, 38 are configured to becoupled to the handpiece 22, allowing the cassette 26 to provide atleast irrigation fluid to, and aspiration of fluid from, the eye E. Insome embodiments, the system 20 handpiece further comprises means foremulsification of the natural lens of the eye E. An ultrasonicallydriven piezoelectric crystal may be used to provide this function;however, other means are consistent with embodiments of the presentinvention, for example, a high energy laser beam. In other embodiments,the handpiece 22 is configured to cut and remove vitreous material inthe posterior chamber of the eye E, for example, by including anelectrically or pneumatically driven cutter blade.

Referring to FIG. 13, in certain embodiments, the ramp 54 is configuredto have an arcuate form that can reduce or substantially eliminate rapidand/or large pressure fluctuations in the aspiration line 38 and the eyeE caused by the peristaltic pump 40. The dotted circle P illustrates anapproximate path of the distal most portions of projections 52 (i.e.,the point or line on each projection 52 that is closest to ramp 54 asthe pump head 50 rotates). In such embodiments, the ramp 54 comprises acentral portion 80 generally configured such that the resilient channel56 is completely sealed or substantially sealed as the projections 52rotate or move along the central portion 80 of the ramp 54. The shape ofthe central portion 80 may be characterized by a base curvatureC_(central) that is generally constant, although the shape of thecentral portion 80 may vary in accordance with particular designrequirements or constraints.

The ramp 54 also comprises an entrance portion 82 having an arcuateextent over which one of the projections 52 closes the resilient channel56 as the projections 52 move by the ramp 54. The entrance portion 82may be characterized by a base curvature C_(entrance) that is differentfrom the base curvature C_(central), preferably less than the curvatureC_(central). The decreased curvature C_(entrance) of the entranceportion 82 may be configured to reduce the rate at which the resilientchannel 56 is compressed, thus reducing or eliminating pressurefluctuations in the aspiration line 38 and eye E. In order to aid in thereduction of pressure fluctuations, the transition between entranceportion 82 and the central portion 80 is made generally smooth, forexample, by configuring the entrance and central portions 82, 80 to betangent at a connection point or line therebetween. The shape of theentrance portion 82 may have a constant curvature; however, as discussedin greater detail below, a more complex shape may advantageously furtherreduce pressure fluctuations at the entrance to the peristaltic pump 40.

The ramp 54 further comprises an exit portion 84 having an arcuateextent and characterized by a base curvature C_(exit) that is differentfrom the base curvature C_(central). The shape of the exit portion 84may have a constant curvature, although the shape may vary in accordancewith particular design requirements or constraints. Advantageously, theextent of the entrance portion 82 is unequal to the extent of the exitportion 84. In the illustrated embodiment, the entrance portion 82 has agreater extent than that of the exit portion 84, for example, to providea greater time and distance over which the resilient channel 56 isgradually squeezed or compressed. By increasing the extent of theentrance portion, the rate at which resilient channel 56 is compressedmay be decreased, thus allowing the pressure fluctuations in theaspiration line 38 to be reduced.

In some embodiments, the smaller extent of the exit portion 84 produce arelatively large or rapid pressure increase at the exit of the pump 40and the resilient channel 56. In general, this will not cause problems,since the exit of the resilient channel is isolated from the aspirationline 38 and the eye E. In some instance, however, the entrance portion82 may actually have a smaller extent than that of the exit portion 84,depending upon the choices of a particular designer.

As illustrated in FIG. 13, the extent of the portions 80, 82, 84 mayhave generally arcuate extents. These arcuate extents may beapproximately centered about center of the dotted circle P, although itwill be appreciated that portions of the portions 80, 82, 84,particularly of the entrance portion 82, may have very large radii ofcurvature (even infinite) that are centered at great distances from thecenter of the dotted circle P. In some embodiments, the pump 40 may belinear or substantially linear in its operation, in which case theextent of one or more of the portions 80, 82, 84 may be partially orsubstantially linear in nature or have very large radii of curvature.

Again referring to FIG. 13, exit portion 84 of the ramp 54 has anarcuate or angular extent θ_(exit). In some embodiments, the exitportion 84 is substantially linear, in which case the extent is moreappropriately expressed as an linear distance, rather than an angularextent. The central portion 80 of the ramp 54 has an arcuate or angularextent θ_(central) that preferably is much greater than θ_(exit).Generally, the angular extent of the central portion 80 is at least 90degrees in order that at least two of the projections 52 of theperistaltic pump 40 close the resilient channel 56 at any given time orposition of the pump head 50. In some embodiments, the angular extentθ_(central) is 100 degrees or about 100 degrees, for example, when thepump head has four projections 52 that are approximately 90 degreesapart from one another. In other embodiments, the angular extentθ_(central) is between about 90 degrees and about 120 degrees. In yetother embodiments, the angular extent θ_(central) may be less than about90 degrees, for example, when the pump head has five, six, or moreprojections 52 that are approximately evenly space apart from oneanother. Alternatively, the angular extent θ_(central) may be greaterthan 120 degrees, 130 degrees, or even 140 degrees, for example, whenthe pump head has two or three projections 52 that are approximatelyevenly space apart from one another.

The entrance portion 82 of the ramp 54 has a substantially arcuateextent from line 94 to line 96 shown in FIG. 13. The entrance portion 82comprises a proximal portion 100 near the entrance into the pump 40(e.g., at or near the intersection of the ramp 54 with the line 94) anda distal portion 102 near the central portion 82 of the ramp 54 (e.g.,disposed at or near the intersection of the ramp 54 profile with theline 96). The profile of entrance portion 82 generally movesprogressively further from the circle P when moving from the proximalportion 100 to the distal portion 102. In general, proximal portion 100is disposed farther away from the circle P than the distal portion 102.In some embodiments, proximal portion 100 is configured such that whenthe projections 52 of the pump 40 initially engage the resilient channel56, the resilient channel 56 moves away from the circle P and/or towardthe proximal portion 100 of the ramp 54. This may advantageously reduceor eliminate the production of pressure waves or variations in theaspiration line 38 that might otherwise damage the eye E.

The entrance portion 82 of the ramp 54 may comprise adjoining firstsegment 110, second segment 112, third segment 114, and fourth segment116. Each of the segments 110, 112, 114, 116 may have a curvature thatis constant over most of their extents and may include relatively smalltransition portions between each of the segments for providing smoothtransitions therebetween. Alternatively, one or more of the segments110, 112, 114, 116 may comprise a non-circular profile, for example, aprofile that varies slightly from a base curvature with a predeterminedradius of curvature. In the illustrated embodiment, the second segment112 has a curvature that is less than that of the first segment 110. Insome embodiments, the second segment 112 has a curvature of zero (e.g.,a straight line) or nearly zero (e.g., a very large radius ofcurvature). The first and/or second segments 110, 112 may be configuredto provide a predetermined location of the proximal portion 100, so asto provide a desired interaction between the resilient channel 54 andthe projections 52 upon engagement therebetween. The third segment 114has a relatively large curvature that is greater than that of the secondsegment 112. The third segment 114 may be configured provide apredetermined orientation of the proximal portion 100. The fourthsegment 116 has curvature that is less than the curvature of the secondsegment, and is preferably straight, nearly straight, or only slightlyarcuate in shape.

In some embodiments, the cassette housing 32 comprises a front face 88that is substantially symmetrically disposed about a central axis orperpendicular plane. Thus, the front face 88 is substantially normal toa first axis 90, while the central portion 80 is asymmetrically disposedabout the first axis 90. In addition, the central portion 80 may besymmetrically disposed about a second axis 92 that itself is disposed atan angle θ_(offset) relative to the first axis 90 (where positive anglesin FIG. 13 are in a clockwise direction from the first axis 90). In theillustrated embodiment, the angular extent θ_(central) of the centralportion 90 is about 100 degrees and θ_(offset) is about 30 degrees.Generally, the angle θ_(offset) is between about −40 degrees and about+40 degrees, preferably between −30 degrees and +30 degrees. When theentrance portion 82 is configured to have an extent that is greater thanthat of the exit portion 84, θ_(offset) is between about 0 degrees andabout 50 degrees, preferably between about 20 degrees and about 40degrees. The ranges may, of course, change depending on the particulardesign parameters, for example, the number of projections 52 in the head50 of the pump 40.

Referring to FIGS. 14 and 15A-C a method 200 of operating the surgicaltreatment system 20 comprises an operational block 210 of engaging acassette according to embodiments of the present invention (e.g., one ofthe cassettes 26, 26 a, or 26 b) with the console 24 so as to form thepump 40 and to couple the handpiece 22 with the console 24. The method200 also comprises an operational block 220 of rotating at least oneprojection 52 of the peristaltic pump 40 so as to engage a portion ofthe resilient channel 56. The method 200 additionally comprises anoperational block 230 of compressing or closing the resilient channel 56over an extent θ_(entrance) so as to draw in fluid and/or other materialinside the resilient channel 56. The method 200 further comprises anoperational block 240 of maintaining the resilient channel 56 in asealed or closed condition over an extent θ_(central). The method 200also comprises an operational block 250 of expanding or opening theresilient channel 56 over an extent θ_(exit) so as to allow material tobe ejected from the peristaltic pump 40, wherein the extent θ_(entrance)is greater than the extent θ_(exit).

The above presents a description of the best mode contemplated ofcarrying out the present invention, and of the manner and process ofmaking and using it, in such full, clear, concise, and exact terms as toenable any person skilled in the art to which it pertains to make anduse this invention. This invention is, however, susceptible tomodifications and alternate constructions from that discussed abovewhich are fully equivalent. Consequently, it is not the intention tolimit this invention to the particular embodiments disclosed. On thecontrary, the intention is to cover modifications and alternateconstructions coming within the spirit and scope of the invention asgenerally expressed by the following claims, which particularly pointout and distinctly claim the subject matter of the invention.

What is claimed is:
 1. A fluidics cassette, comprising: a housing; anirrigation line and an aspiration line, the lines configured to providedirrigation and aspiration functions for an eye treatment probe; a rampconfigured for transferring fluid through a resilient channel when theresilient channel is engaged between the ramp and one or more of aplurality of projections of a pump head, the ramp comprising: a centralportion characterized by a first base curvature at which the resilientchannel is completely sealed as the plurality of projections rotatealong the central portion; an entrance portion characterized by a secondbase curvature that is different from the first base curvature andhaving an extent over which one of the projections closes the resilientchannel as the projection moves by the ramp; and an exit portioncharacterized by a third base curvature that is different from the firstbase curvature and having an extent less than that of the entranceportion for producing a rapid pressure increase; wherein the second basecurvature of the entrance portion being unequal to the third basecurvature of the exit portion, wherein the portion of the ramp that isconfigured to engage the pump head has an arcuate shape from a beginningof the entrance portion through the central portion to an end of theexit portion.
 2. The fluidics cassette of claim 1, wherein the resilientchannel is disposed within the aspiration conduit.
 3. A fluidicscassette, comprising: a housing comprising a front face disposedsubstantially normal to a first axis; an irrigation conduit and anaspiration conduit, the conduits configured to provided irrigation andaspiration functions for an eye treatment probe; a ramp configured fortransferring fluid through a resilient channel when the resilientchannel is engaged between the ramp and one or more of a plurality ofprojections of a pump head, the ramp comprising: a central portioncharacterized by a first base curvature at which the resilient channelis completely sealed as the plurality of projections rotate along thecentral portion; an entrance portion characterized by a second basecurvature that is different from the first base curvature and having anextent over which one of the projections closes the resilient channel asthe projection moves by the ramp; the central portion beingasymmetrically disposed about the first axis.
 4. The fluidics cassetteof claim 3, wherein the central portion is symmetrically disposed abouta second axis, the second axis disposed at a predetermined anglerelative to the first axis.
 5. The fluidics cassette of claim 4, whereinthe central portion has an arcuate extent of about 100 degrees and thepredetermined angle is about 30 degrees.
 6. The fluidics cassette ofclaim 3, wherein the front face is disposed substantially symmetricallyabout the first axis.
 7. A fluidics cassette, comprising a housing; anirrigation conduit and an aspiration conduit, the conduits configured toprovided irrigation and aspiration functions for an eye treatment probe;a resilient tube configured to transfer fluid from when engaged by aplurality of projections of a pump head; a first keyed insert disposedalong an input portion of the resilient tube; a second keyed insertsubstantially congruent with the first keyed insert and disposed alongan output portion of the resilient tube; a first keyed receiver coupledwith the housing; and a second keyed receiver coupled with the housing;wherein the first keyed insert and second keyed insert having the sameorientation when the tube is in an unstressed condition; and wherein thefirst and second keyed inserts being configured to orient the resilienttube with a ramp when coupled with the first keyed receiver and thesecond keyed receiver, wherein the first and second keyed inserts eachhave a shape and the first and second keyed receivers each have aninternal shape that corresponds to the shape of their respective keyedinserts, and wherein the first and second keyed inserts are configuredto only couple with the first and second keyed receivers in a singleorientation.
 8. A fluidics cassette of claim 7, further comprising aramp configured for transferring fluid through the resilient tube as theprojections move by the ramp.
 9. A fluidics cassette of claim 7, whereinthe housing comprises a pair of cavities disposed to receive the firstkeyed insert and the second keyed insert.
 10. A fluidics cassette ofclaim 9, wherein the spacing between the first keyed insert and thesecond keyed insert is selected to provide a predetermined tension ofthe resilient tube as the projections move by the ramp.
 11. The fluidicscassette of claim 1, wherein the second base curvature is less than thefirst base curvature.